Motorized vehicles include a powertrain operable to propel the vehicle and power the onboard vehicle electronics. The powertrain, or drivetrain, generally includes an engine that powers the final drive system through a multi-speed power transmission. Many vehicles are powered by a reciprocating-piston-type internal combustion engine (ICE). The internal combustion engine converts chemical energy stored in fuel (gasoline, diesel, bio fuels, natural gas, or other fuels) into kinetic energy through combustion of the fuel mixed with air.
Hybrid vehicles utilize multiple, alternative power sources to propel the vehicle, minimizing reliance on the engine for power. A hybrid electric vehicle (HEV), for example, incorporates both electrical energy and chemical energy, and converts the same into mechanical power to propel the vehicle and power the vehicle systems. The HEV generally employs one or more electric machines (motor/generators) that operate individually or in concert with the internal combustion engine to propel the vehicle. The electric machines convert kinetic energy into electrical energy which may be stored in an energy storage device. The electrical energy from the energy storage device may also be converted back into kinetic energy for propulsion of the vehicle.
During operation, the various components may generate heat through energy conversion and operational inefficiencies. In some instances, the hybrid vehicle powertrain may be capable of a maximum efficiency when operated within a particular temperature range. When the powertrain is colder than desired, viscous friction and temperature-dependent electrical resistances may result in inefficient operation. Conversely, when the powertrain is hotter than desired, components may experience accelerated wear and liquids may be at an increased risk of vaporizing. It is common to use active cooling systems in an attempt to modulate the temperature of the powertrain, as sensed by temperature probes disposed across the various vehicle components.